Cholesterol, Lipoprotein Metabolism And Steroids Flashcards
Organic compound with four fused rings arranged in a specific configuration (ABCD ring system)
Steroids
A subgroup of steroids with a hydroxyl group at the 3-position of the A-ring
Sterol
Cholesterol structure
HO-A ring-B ring-C ring-D ring-hydrocarbon tail
Is cholesterol hydrophilic or hydrophobic?
Hydrophobic
What is the major sterol in animal tissues?
Cholesterol
Cholesterol is a precursor for the synthesis of what 3 compounds?
Bile salts
Steroid hormones
Vitamin D
Cholesterol function
Essential structural component of animal cell membranes (30%)
required to maintain both membrane structural integrity and fluidity at different temperatures
Enables animal cells to dispense within cell shape in order to protect membrane integrity and cell viability
Components of lipid rafts formation to facilitate cell signaling
Where is free cholesterol found?
Membranes of animal cell membranes
Free cholesterol is..
Unesterified. Hydroxyl group on A-ring
Esterified cholesterol is…
Esterified, or cholesteryl ester. A-ring has a fatty acid attached to the Oxygen
Are esterified cholesterol in the membranes?
Nope
Where are esterified cholesterol found?
Plasma. Most plasma cholesterol is in this form.
What cells a can synthesize cholesterol?
Most, but significantly from Liver, Intestine, and steroidogenic tissues.
Steroidogenic=adrenal cortex, testes, ovaries
What organs controls the overall cholesterol homeostasis?
Liver (synthesis, distribution, and elimination)
Sources of liver cholesterol
De novo synthesis
Diet
HDLs
Routes for cholesterol clearance from the liver
Secretion into VLDL/LDL
What leads to gradual deposition of cholesterol in the tissues?
The balance between cholesterol influx and efflux isn’t precise
Where does the cholesterol typically deposit?
Endothelial linings of blood vessels
Lipid depositions over time leads to
Plaque formation
Plaque formation, from lipid deposition, causes what?
Atherosclerosis. The narrowing of blood vessels
Atherosclerosis is important because
It causes an increased risk of cardio, cerebro, and peripheral vascular disease
May be life-threatening.
Substrates for Cholesterol Synthesis
Acetyl CoA
NADPH
ATP
cholesterol synthesis will occur under what conditions?
In well-fed state (when the substrates are available)
When the cholesterol supply is low
Synthesis of Cholesterol occurs in the…
Hepatocytes